There are a number of DTML tags, each of which begins with dtml-. Most DTML tags take one or more parameters, where each parameter allows it to work in a slightly different way. For example, we can modify our test document to include a simple use of <dtml-var expr>:
The value of our expr in the above code is a simple Python expression. Zope evaluates the expression and replaces the dtml-var tag with the result of that evaluation. We also can try something more interesting than simple addition. For example, we can use the capitalize method in the string module (automatically imported into Zope) by naming it in the expr attribute:
<p><dtml-var expr="_.string.capitalize('abc')"></p>Notice how we cannot invoke string.capitalize(), but must rather invoke _.string.capitalize().
While DTML allows you to use the string module in this way, you may never have to invoke it directly because so many useful string functions are built into DTML.
DTML was made for designers and other nonprogrammers to be able to create their own dynamic content without being stuck with the poor syntax and documentation of server-side includes. DTML is not as easy for nonprogrammers to learn as some of us might think, but it is far easier than teaching them a full-fledged programming language. And the fact that Zope performs some error checking when saving the DTML document helps to avoid some of the issues associated with runtime languages.
This month, we took a whirlwind tour of several of Zope's features, including through-the-web editing, the management interface, acquisition and simple DTML documents. Next month, we will look at Zope products—how to download and install them, and then how to write our own.